Fix a large number of typos and other problems (#110)

Most of these fixes are for typos and extra whitespace at the
end of lines. These are the notable changes:
- Fixed a compatibility issue with how asterisks are displayed
  using certain fonts. Bug report: https://github.com/att/ast/issues/764
- Fixed a bug in the man page that caused searches for the '|'
  character to fail. Bug report: https://github.com/att/ast/issues/871
- Removed a duplicate description of 'set -B' from the man
  page. Bug report: https://github.com/att/ast/issues/789
- Added documentation for options missing from the ksh man
  page (applies to 'hist -N', 'sleep -s', 'whence -q' and
  many of ulimit's options). Bug reports:
  https://github.com/att/ast/issues/948
  https://github.com/att/ast/issues/503#issuecomment-386649715
  https://github.com/att/ast/issues/507#issuecomment-507924608
- Applied the following ksh2020 documentation fixes:
  https://github.com/att/ast/pull/351
  https://github.com/att/ast/pull/352
- Fixed a minor GCC -Wformat warning in procopen.c by changing
  a sentinel to NULL.

src/lib/libast/man/stk.3

@@ -57,14 +57,14 @@ install it as the active stack.
 A stack is created with the \f5stkopen\fP() function.
 A \fIflags\fP argument of \f5STK_SMALL\fP indicates that unused
 space on the stack should be freed whenever this stack ceases
-to be the active stack. 
+to be the active stack.
 If successful,
 \f5stkopen\fP() returns a pointer to a stack whose reference
 count is 1.
 Otherwise, \f5stkopen\fP() returns a null pointer.
 The \f5stklink\fP() function increases the reference count for the
 given \fIstack\fP.
-The \f5stkinstall\fP() function 
+The \f5stkinstall\fP() function
 makes the specified \fIstack\fP the active stack and returns a pointer
 to the previous active stack.
 When the \fIoverflow\fP argument is not null,
@@ -115,7 +115,7 @@ stack the result is undefined.
 .PP
 The \f5sfio\fP(3) output functions can be used to build
 current object incrementally.
-An object that is built incrementally on the stack will  
+An object that is built incrementally on the stack will
 always occupy contiguous memory within a stack frame but
 until \f5stkfreeze\fP() is called,
 the location in memory for the object can change.
@@ -125,7 +125,7 @@ Initially, this offset is zero, and the offset changes as a result
 of the operations you specify.
 The \f5stkseek\fP() function is used set the offset for the
 current object.
-The \fIoffset\fP argument to \f5stkseek\fP() specifies the new 
+The \fIoffset\fP argument to \f5stkseek\fP() specifies the new
 offset for the current object.
 The frame will be extended or moved
 if \f5offset\fP causes the new current offset to extend beyond the